Automatic choke



J. SKUDELNY AUTOMATIC CHOKE Filed April 12, 1963 3 Sheets-Sheet 1 A TTOR/Vfy Aug- 3, 1965 J. SKUDELNY 3,198,186

AUTOMATIC CHOKE Filed April l2, 1963 5 Sheets-Shea? 2 e e 24 |'/2 I /7 /3 /`9 l l 7 i ,2/ I 4` 41 9' J. SKUDELNY AUTOMATIC CHOKE Aug. 3, 1965 3 Sheets-Sheet 5 Filed April l2, 1963 JOACHIM SKUDELNV uw?? Egg/MMM A'l'l'ORN EYS United States Patent O 3,1%86 AUTOMA'HC CHKE Joachim Skudeluy, Coiogne, `Germany, assigner to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Apr. i2, .1963,Ser. No. 272,657 4 Claims. (Cl. l23-1ll9) This invention relates to an automatic choke for the induction system of an internal combustion engine.

The typical automatic choke employs a thermally rcsponsive spring for positioning the choke valve in response to temperature variations. `The thermally responsive spring is convention-ally supported upon the charge forming device of the engine and may actuate the choke valve either by means of a direct connection or through a lever and linkage arrangement. The thermally responsive spring is heated by the engine so that its temperature has a relationship to the engine temperature.

In one method frequently employed to heat the thermally responsive spring, air that has been heated through contact with the exhaust manifold of the engine is circulated around the thermally responsive spring. There is a distinct disadvantage to the use of exhaust heat. The thermally responsive spring cools rapidly when the engine is stopped. Upon restarting an engine that has been stopped for only a short interval, the thermally responsive spring will have cooled and closed the choke valve even though the engine itself may be thoroughly warm. This results in an unnecessarily rich mixture and t `does not come on as rapidly when a thoroughly warmed engine is stopped.

Since the automatic choke mechanism is normally positioned a considerable distance away from the liquid cooled portions of the engine, it has been necessary to provide a coolant jacket on the choke assembly for the thermally responsive spring. Hoses and hose connections are required to circulate the coolant from the engine to the coolant jacket of the automatic choke. The additional conduit and coolant jacket adds considerable cost to the choke mechanism. The coolant jacket also presents the undesirable disadvantage of heating the carburetor. The heating of the carburetor causes such hot fuel handling problems as vapor lock.

It has been proposed to eliminate the choke coolant jacket and attendant conduits by positioning the thermally responsive element in contact with or adjacent to a portion of the cooling system of the engine. This necessitates the provision of a linkage system #to actuate the remotely positioned choke valve. The linkage systems employed involve considerable cost penalty inasmuch as they must be built to close tolerances and require frequent adjustment.

It is, therefore, the principal object of this invention to provide an automatic choke mechanism in which the choke valve is positioned in accordance with the actual operating temperature of the engine.

lt is a further object of this invention fte provide an automatic choke mechanism that permits sensing of the engine temperature at a position remote from the choke valve without necessitating complicated actuating linkages.

An automatic choke for the induction system of an internal combustion engine comprising this invention inice cludes a choke valve rotatably supported in an induction passage. A pressure responsive device is operably connected to the choke valve for positioning the choke valve in response to pressure changes. A closed conduit extends from a portion of the engine heated by its operation to the pressure responsive device. Thermal expansion of a fluid constrained within the conduit generates -an actuating pressure on the pressure responsive device in response to increases in engine temperature.

Further objects and advantages of this invention Will become more apparent as this description proceeds particularly when considered in conjunction With the accompanying drawings, wherein:

FTGURE l is a cross sectional view taken through portions oi an internal engine embodying this invention, showing the choke valve in a closed position.

FIGURE 2 is a cross sectional view taken along line 2 2 of EGURE l.

FiGURE 3 is a cross sectional view, in part similar to FIGURE l, showing the choke valve in a partially opened position.

FIGURE 4 is a cross sectional view, in part similar to FIGURES l and 3, showing the choke valve fully opened.

FIGURE 5 is a partial perspective view of an internal combustion engine embodying this invention.

In the drawings, to which detailed reference is now made, the pertinent portions of an internal combustion engine embodying this invent-ion are illustrated. A charge forminrY device, indicated generally at il, is formed with an induction passage l2. A choke valve shaft 13 is rotatably journaled in fthe charge forming device l1 and supports a choke valve 1li in the induction passage l2. The choke valve i4 is supported in the induction passage t?. anterior to the throttle valve and fuel discharge elements which are conventional and, accordingly, are

not shown.

At one side ofthe charge forming device 11 the choke valve shaft i3 extends outwardly and has aiiixed thereto `a biturcated lever l5 having outwardly extending arms ld and l'. A spiral shaped Bourdon tube 18 has its open end afrixed to the body of the charge forming device il, as at i9. The closed end of the Bourdon tube 1S is aihxed to a lever 2l. The lever Zi may be rotatably journaled in any suitable manner (not shown). A pin 22 xed to the end of the lever 2l normally engages a slot 23 formed in the arm 16 ot the bifurcated lever l5.

Changes in pressure within the Bourdon tube i8 Will cause it to coil or uncoil and rotate the lever 2l Ito position the choke valve le through the contact of the pin 22 with the arm i6 of the bifurcated lever l5. The pressure Within the Bourdon tube 1S is varied dependent upon the operating temperature of the engine in the manner now to be described.

The open end of the Bourdon tube i8 extends into a small diameter tube 2li. The tube 2d extends from fthe charge forming device il to a portion ot the engine that is heated in response to its operation. in the illustrated embodiment, the tube 24 terminates adjacent to a cylinder head 25 of the engine. A cavity 26 is formed within the cylinder head 25 adjacent to a liquid cooling jacket 27. It has been found desirable to sense the temperature of the engine at the cylinder head inasmuch as the cylinder head temperature is most representative of the actual operating conditions of the engine. The cavity 26 is closed by a fitting 2S that is affixed to the end of the tube 24. A thermally expansible fluid such as air is conined in the duid circuit defined by the Bourdon tube 18, the tube 2d and the cavity 26.

When the engine is cold the iiuid confined within the Bourdon tube iii, tube 24 and cavity 26 will contract. This permits the Bourdon tube 18 to coil because of its resilience and rotate the lever 2l in a clockwise direction.

'clockwise direction to open the choke valve 14.

The arm 16 of fthe lever 15 is also rotated in a clockwise direction because of the action of a torsional spring 29 that encircles choke valve shaft 13 (FEGURE 2.). The clockwise rotation of the lever 15 and the choke valve shaft-13 closes the choke valve 14 in the induction passage 12 (FIGURE 1). During cranking of the cold engine, the choke valve 14 remains shut fto cause a rich fuel mixture to be drawn into the induction :systern of the engine.

When the engine starts, it is desirable to have the choke valve 14 open slightly to permit sufiicienit air flow for enigne operation. For this purpose a vacuum operated piston 31 is provided. The piston 3l is received in a bore 32 formed in the body of the charge forming device lll. The lower end of the bore 32 is exposed to intake manifold vacuum through a conduit 33. When the engine commences to run, a decrease in pressure occurs in the conduit 33and bore 32. This draw-s the piston 3i downward (FIGURE 3). The motion of the piston 3l is transmitted by a link 3,4 to the arm il? of the lever l5. The resulting counterclockwise rotation of the arm 17 rotates the choke valve shaft 13 and opens the choke valve 14 slightly. It desired, the choke valve 14 may additionally be unbalanced so that the pressure diiterential across the choke valve also causes it to open.

As the temperature of the coolant in the jacket 27 increases, the heat will be conducted through the cylin- -der head 25 to the cavity 26. As the temperature of the Huid in the cavity 26 is raised, its volume increases to exenta pressure through the tube 24 upon the Bourdon tube l. The increased pressure in the Bourdon tube 13 causes it to uncoil and rotate the leve-r 21 in a counterclockwise direction. The action of the pin 22 in the slot 23 rotates the `arrn 16 of the lever 1S in a counter- The expansion of the iiuid and uncoiling of the Bourdon tube 18 continues until the choke valve 14 has been rotated to its fully opened position (FIGURE 4).

It is to be understood that the embodiment illustrated and described is only exemplary of a preferred form of the invention. Structures other than that illustrated may be employed to practice the invention. For example, it is possible to iix the closed end of the Bourdon tube to the charge forming device and to utilize the open end for actuating the choke valve. The manner and location chosen for sensing the engines temperature may also be varied. Other changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Whait is claimed is:

1. An automatic choke for the induction system of an internal combustion engine comprising a choke Valve rotatable in an induction passage of the induction system, a Bourdon tube, means connecting the closed end of said Bourdon tube tto said choke valve for moving said choke valve between a closed and an open position in response to pressure changes, a conduit closing the other end of said Bourdon tube and extending to a portion of the engine heated by its operation, and a iiuid coniined in said conduit and said Bourdon tube, said fluid being thermally expansible to generate an actuating pressure upon said Bourdon tube in response to increases in temperature caused by the operation of the engine.

2. In an internal combustion engine having an induction system including a charge forming device, a choke valve rotatable in an induction passage of said charge forming device, a Bourdon tube supported by said charge forming device contiguous to the choke valve, 4a chamber positioned in heat exchanging relation to a portion of the engine that is heated by its operation, means operably connecting the closed end of said Bourdon tube to said choke valve for moving said choke valve between -a closed and -an open position in response to pressure changes, a conduit extending from the open end of said Bourdon tube to close said chamber and deiine a closed fluid circuit, and a fluid confined in said circuit, said iiuid being thermally expansible to generate an actuating pressure upon said Bourdon tube in response to increases in tempearture caused by the operation of the engine.

3. In an internal combustion engine having an induction system including a charge forming device7 a choke valve rotatably supported by .a choke valve shaft in an induction passage of said charge forming device, a lever affixed to said choke valve shaft, a Bourdon tube having its open end supported by said charge forming device, means operably connecting the closed end of said Bourdon tube to said lever to move said choke valve between a closed and an open position in response to pressure changes within said Bourdon tube, a chamber positioned in heat exchanging relation to a portion of the engine that is heated by its operation, said chamber being spaced from said Bourdon ltube and from said choke valve shaft, a conduit closing said chamber and extending from said chamber to the open end of said Bourdon tube to form a closed fluid conduit, and a fluid confined in said circuit, said iiuid being thermally expansible to generate an actuating pressure upon said Bourdon tube in response to increases in temperature caused by the operation of the engine.

4. An internal combustion engine as dened by claim 2 wherein a suction motor is operatively connected to said choke valve for modulating the effect of said Bourdon tube upon said choke valve and a pressure connection extends between said suction motor and said induction passage posterior to said choke valve for partially opening said choke valve upon increases in engine induction system suction.

References Cited by the Examiner UNITED STATES PATENTS 2,362,346 11/44 Blake 123-119 2,774,343 12/56 Schaffer 123-119 KARL J. ALBRECHT, Primary Examiner. 

1. AN AUTOMATIC CHOKE FOR THE INDUCTION SYSTEM OF AN INTERNAL COMBUSTION ENGINE COMPRISING A CHOKE VALVE ROTATABLE IN AN INDUCTION PASSAGE OF THE INDUCTION SYSTEM, A BOURDON TUBE, MEANS CONNECTING THE CLOSED END OF SAID BOURDON TUBE TO SAID CHOKE VALVE FOR MOVING SAID CHOKE VALVE BETWEEN A CLOSED AND AN OPEN POSITION IN RESONSE TO PRESSURE CHANGES, A CONDUIT CLOSING THE OTHER END OF SAID BOURDON TUBE AND EXTENDING TO A PORTION OF THE ENGINE HEATED BY ITS OPERATION, AND A FLUID CONFINED IN SAID CONDUIT AND SAID BOURDON TUBE, SAID FLUID BEING THERMALLY EXPANSIVE TO GENERATE AN ACTUATING PRESSURE UPON SAID BOURDON TUBE IN RESPONSE TO INCREASES IN TEMPERATURE CAUSED BY THE OPERATION OF THE ENGINE. 